External battery pack

ABSTRACT

An external battery pack is provided. The external battery pack includes a secondary battery, an internal circuit, a housing having the secondary battery and the internal circuit, and an inserting portion. The inserting portion is formed in the housing, and the inserting portion is capable of inserting and fixing a portable electronic device. In addition, the external battery pack preferably further includes a pen type fixing unit having a holding part and the inserting portion preferably includes a supporting portion and an inserting rib.

TECHNICAL FIELD

The present invention relates generally to an external battery pack and,more particularly, an external battery pack having a pen type fixingunit in a housing for carrying comfortably and potably and acharging/outputting circuit unit having a controlling function ofconstant voltage and constant current, thereby supplying driving powersource with a portable electronic device and concurrently charging aninternal battery pack of the portable electronic device.

BACKGROUND ART

Generally, a rechargeable battery such as a Lithium-ion (Li⁺) battery, aNickel—Cadmium (Ni—Cd) battery, and a Nickel-Metal hybrid (Ni-MH)battery, which is can be used for being semi-permanent, is called asecondary battery.

The demand of the secondary battery is greatly increased as increasing aportable electronic device usage such as a portable computer, acamcorder, a cellular phone, and etc.

However, as the portable electronic device has high performance andmultiple functions, driving power source needed to the portableelectronic device can be insufficient. Further, the capacity of aninternally installed battery may be limited to increase because of beinga smaller and slimmed portable electronic device. In addition,supplementary power source (or an external battery pack) is needed forsupplying sufficient driving power source with the electronic device.

A conventional external battery pack generally uses an output circuithaving a function of constant voltage control and supplies power sourcewith the portable electronic device through an input terminal of analternating current/direct current adapter (AC/DC adapter) therein.However, in case that the device dose not have an AC/DC adapter or thedevice has an input terminal directly connected to an internallyinstalled battery pack for supplying power source, it is impossible touse the conventional external battery pack.

In addition, as the portable electronic device is generally used forouting, an external battery pack concurrently used with the portableelectronic device should be portably comfortable. Instead, theconventional external battery pack is not comfortable for portablycarrying.

Further, as the conventional external battery pack has a chargingcircuit unit and an output circuit unit as separated circuit unit, it isnot easy to make a smaller external battery pack and it is noteconomical.

It is therefore an object of the present invention to provide anexternal battery pack including a pen type fixing unit in a housing forfixing at clothing or a belt and an inserting unit for inserting andfixing a portable electronic device, and having a hands-free function,thereby providing a portable and comfortable external battery pack.

It is another object of the present invention to provide an externalbattery pack including a charging/outputting unit and a circuitconverting connector for selecting an internal circuit according to ausing condition.

DISCLOSURE OF THE INVENTION

To achieve the objects of the present invention, an external batterypack preferably includes a secondary battery, an internal circuit, and ahousing having the secondary battery and the internal circuit, aninserting portion is formed in the housing, and the inserting portion iscapable of inserting and fixing a portable electronic device.

In addition, the external battery pack preferably further includes a pentype fixing unit having a holding part, the pen type fixing unit isformed at a rear side of the housing for being held on clothing or abelt. The inserting portion preferably includes a supporting portion ona front bottom side of the housing and an inserting rib on both lateralsides of the housing.

According to a preferred embodiment of the present, the insertingportion preferably further includes a fixing hook capable of moving in avertical direction. The inserting portion further includes a detachingprotection portion capable of moving up and down, the detachingprotection portion is connected to an elastic material installed in thehousing.

Furthermore, a portable electronic device or a battery therein caninclude a few circuit parts selected from the internal circuit partsincluded in the external battery pack according to an embodiment of thepresent invention. Therefore, the internal circuit included in theexternal battery pack can be made various types excepting a few circuitsincluded in the portable electronic device or the battery therein.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the present invention willbecome more apparent by describing in detail preferred embodimentsthereof with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of an internal circuit in an external batterypack according to an embodiment of the present invention;

FIG. 2 is a block diagram of an internal circuit connection duringcharging a secondary battery in an external battery pack according to anembodiment of the present invention;

FIG. 3 is an block diagram of an internal circuit connection duringoutputting power source from an external battery pack to a portableelectronic device according to an embodiment of the present invention;

FIG. 4 is a diagram showing a charging method of a Lithium-ion secondarybattery;

FIG. 5 is a schematic diagram of a housing of an external battery packaccording to an embodiment of the present invention;

FIG. 6 is a schematic diagram of a housing of an external battery packaccording to another embodiment of the present invention; and

FIG. 7 is a schematic diagram of a housing of an external battery packaccording to another embodiment of the present invention.

DESCRIPTION OF THE NUMERALS OF DRAWINGS

-   10 secondary battery-   20 charging connector-   30 charging/outputting circuit unit-   31 charging circuit unit-   32 output circuit unit-   40 protection circuit unit-   50 DC/DC voltage converting circuit unit-   60 power source output connector-   70 battery remaining display circuit unit-   80 battery remaining display unit-   90 pen type fixing unit-   100 supporting portion-   110 inserting rib-   120 inserting unit-   130 hands-free selection unit-   140 speaker-   150 microphone-   160 circuit converting male connector-   170 circuit converting male connector-   180 detaching protection jaw-   190 connection bar-   200 detection protection unit-   210 groove-   220 spring-   225 fixing hook-   230 pin-   d1 first diode-   d2 second diode

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout. Moreover, each embodimentdescribed and illustrated herein includes its complementary conductivetype embodiment as well.

An external battery pack according to an embodiment of the presentinvention will be described by using the attached drawings.

FIG. 1 is a block diagram of an internal circuit in the external batterypack according to an embodiment of the present invention. FIG. 1 showsan internal circuit according to an embodiment of the present invention,but a few circuits of the internal circuits cannot be included accordingto embodiments.

The process of charging and discharging of the external battery packaccording to an embodiment of the present invention is described byusing FIG. 1.

Referring to FIG. 1, the external battery pack includes a secondarybattery 10 and a charging connector 20 connected to an external powersource by an extension cable (not shown) for supplying power source.

The external battery pack further includes a charging circuit unit 31connected to the charging connector 20. The charging circuit unit 31converts the supplied power source into a given level of current andvoltage for the secondary battery 10 and supplies the converted powersource with a protection circuit unit 40.

When the secondary battery 10 is over-charged by supplying exceededlimiting voltage, an organic electrolyte in the secondary battery 10 isdecomposed by a decomposition reaction. In contrary, the secondarybattery 10 is over-discharged, internal resistance can be increased,thereby deteriorating performance and lowering safety of the secondarybattery 10. The protection circuit unit 40 detects the over-charging andover-discharging for the secondary battery 10, disconnects the externalcircuit, and protects the secondary battery 10 by protecting theover-charging and over-discharging.

The power source having a given level of current and voltage convertedfrom the charging circuit unit 31 and the protection circuit unit 40 ischarged into the secondary battery 10.

A DC/DC voltage converting circuit unit 50 converts the charged powersource in the secondary battery 10 into another power source suitablefor a portable electronic device (not shown).

The charged power source in the secondary battery 10 is supplied to anoutput circuit unit 32 via the DC/DC voltage converting circuit unit 50.

The output circuit unit 32 performs a constant voltage control and aconstant current control to keep the inputted voltage and current fromthe DC/DC voltage converting circuit unit 50 being constant. Thus, theexternal battery pack can supply a driving power source with theportable electronic device and concurrently charge an internal batterypack (not shown) included in the portable electronic device.

According to an embodiment of the present invention, the externalbattery pack further includes a power source output connector 60. Thepower source output connector 60 is electrically connected to a powersource input terminal (not shown) or a battery charging connectingterminal (not shown) of the portable electronic device to supply thepower source which is controlled to the constant voltage and theconstant current.

According to an embodiment of the present invention, the externalbattery pack further includes a battery remaining display circuit unit70 and a battery remaining display 80. The battery remaining displaycircuit unit 70 detects battery remaining status with given steps andcontrols to display the battery remaining status in the batteryremaining display 80. The battery remaining display 80 can include acolor or a mono light emitting diode (LED) for differently displayinglight emitting colors according to charging status. Further, the batteryremaining display 80 can include a plurality of LEDs for displayingcharging status according to a number of the LEDs being “ON”. Forexample, when the charging status is divided into 4 stages, the numberof LEDs is four. When four LEDs are “ON”, it indicates that the batteryis substantially fullly charged. When two LEDs are “ON”, it indicatesthat the battery is substantially half charged.

According to an embodiment of the present invention, the externalbattery pack can include different elements, various embodiments will bedescribed below.

In case that the external battery pack of the present invention canreceive power source and can be connected to a portable electronicdevice or a battery of the portable electronic device, the externalbattery pack according to an embodiment of present invention can includesome elements among the charging circuit unit 31, the protection circuitunit 40, the DC/DC voltage converting circuit unit 50, and the outputcircuit unit 32. That is, the external battery according to anembodiment of present invention can be configured not to include all ofthe above elements, but can be configured to include their combinations.

When the charged power source itself of the secondary battery 10 in theexternal battery pack is used, the external battery pack according to anembodiment of present invention can only include the charging connector20, the charging circuit unit 31, and the power source output connector60.

When constant voltage corresponding to an input of an AC/DC adapter isused, the external battery pack according to an embodiment of presentinvention can further include the DC/DC voltage converting circuit unit50. When a portable electronic device uses constant voltage/constantcurrent for charging the secondary battery 10, the external battery packcan further include the output circuit unit 32.

In case that external power source suitable for charging the secondarybattery 10 is supplied, the external battery pack can only include thecharging connector 20, the DC/DC voltage converting circuit unit 50, andthe power source output connector 60. In case that the portableelectronic device uses constant voltage/constant current for chargingthe secondary battery 10, the external battery pack can further includethe output circuit unit 32.

For the above embodiments, the external battery pack can further includethe protection circuit unit 40 for electrically protecting the secondarybattery 10.

In a simple case, it is possible that the external battery pack can onlyinclude the secondary battery 10.

According to another embodiment of the present invention, the chargingcircuit unit 31 and the output circuit unit 32 can be combined and theexternal battery pack further includes a circuit changing connector forchanging a wiring connection of the internal circuit according to anusage. Detailed embodiments will be described by referring to FIGS. 2and 3.

FIG. 2 is a block diagram of an internal circuit connection duringcharging the secondary battery in the external battery pack according toan embodiment of the present invention.

In this embodiment, a circuit changing connector is comprised of acircuit converting male connector 160 and a circuit converting femaleconnector 160.

The circuit converting female connector 170 includes an a′ terminal, ab′ terminal, a c′ terminal, a d′ terminal, and an e′ terminal. The a′terminal is connected to the protection circuit unit 40. The b′ terminalis connected to a cathode of a first diode d1, wherein an anode of thefirst diode d1 is connected to a charging/outputting circuit unit 30.The c′ terminal is connected to the DC/DC voltage converting circuitunit 50. The d′ terminal is connected between a second diode d2 and thecharging/outputting circuit unit 30. The e′ terminal is connected toground.

The circuit converting male connector 160 includes a, b, c, d, and eterminals corresponding to the a′, b′, c′, d′, e′ terminals,respectively, of the circuit converting female connector 170.

The d terminal of the circuit converting male connector 160 is connectedto a positive terminal V_(IN) ⁺ of the charging connector 20, and the eterminal of the circuit converting male connector 160 is connected to anegative terminal V_(IN) ⁻ of the charging connector 20 and a negativeterminal of the power source output connector 60.

The connection of the a, b, and c terminals of the circuit convertingmale connector 160 and the positive terminal of the power source outputconnector 60 can be varied according to the use of the secondary battery10.

As shown in FIG. 2, when the secondary battery 10 is charged, the aterminal and the b terminal of the circuit converting male connector 160are connected. Then, charged current inputted from the positive terminalV_(IN) ⁺ of the charging connector 20 is sequentially flowed to the dterminal, the d′ terminal, a node f located between the diode D2 and thecharging/outputting circuit unit 30, the charging/outputting circuitunit 30, the first diode d1, the b′ terminal, the b terminal, the aterminal, the a′ terminal, the protection circuit unit 40, and thesecondary battery 10, thereby charging the secondary battery 10.

FIG. 3 is a block diagram of an internal circuit connection duringoutputting power source from the external battery pack to the portableelectronic device according to an embodiment of the present invention.

When power source is outputted to the portable electronic device, the aterminal and the c terminal of the circuit converting male connector 160are connected and the b terminal of the circuit male connector 160 isconnected to the positive terminal V_(OUT) ⁺ of the power source outputconnector 60. Then, discharging current from the secondary battery 10 issequentially flowed to the protection circuit unit 40, the a′ terminal,the a terminal, the c terminal, the c′ terminal, the DC/DC voltageconverting circuit 50, the second diode d2, the charging/outputtingcircuit unit 30, the first diode d1, the b′ terminal, the b terminal,the positive terminal V_(OUT) ⁺ of the power source output connector 60,thereby supplying the power source with the portable electronic device.

The switching operation as described above for connecting betweenterminals is performed by a user. Further, the switching operation isautomatically performed to connect the a terminal and the b terminalwhen the power source is inputted from the charging connector 20 asshown in FIG. 2. The switching operation is automatically performed toconnect the a terminal and the c terminal, and the b terminal and thepositive terminal V_(OUT) ⁺ of the power source output connector 60 asshown in FIG. 3 when power source is not supplied. According to anembodiment of the present invention, the connections as described aboveare examples and connections of the terminals in the circuit convertingmale connector 160 during charging and outputting can be varied and arenot limited. Furthermore, it is possible to make one circuit convertingconnector (not shown) united from the circuit converting male connector160 and the circuit converting female connector 170.

FIG. 4 is a diagram showing a charging method of a Lithium-ion (Li⁺)secondary battery.

As shown in FIG. 4, it is well known in the art that as the Lithium-ionbattery is charged during a short period, it is charged by constantcurrent in a first period of charging, and when charging voltage isreached in a given voltage, it is charged by constant voltage, therebysafely fully charging the battery.

FIG. 5 is a schematic diagram of a housing of the external battery packaccording to an embodiment of the present invention. FIG. 5(a) is alateral diagram of the housing of the external battery pack and FIG.5(b) is a front diagram of the housing of the external battery pack.

The housing includes the secondary battery and a plurality of circuitunits therein, and further includes a pen type fixing unit 90 at onebottom side of the housing for fixing at clothing or a belt.

The pen type fixing unit 90 is made of material having a givenelasticity, so as not to be detached from the clothing or the belt. Thepen type fixing unit 90 preferably includes a hook at an opposite endthe pen type fixing unit 90 connected to the housing.

In FIG. 5, the charging connector 20, the power source output connector60, and the battery remaining display 80 are formed at a long lateralside of the housing, but it can be formed at a short lateral side nearthe pen type fixing unit 90 or at a bottom side of the housing. Further,the charging connector 20, the power source output connector 60, thebattery remaining display 80, and a hands-free selection unit 130 can beformed at different sides, respectively.

According to an embodiment of the present invention, the hands-freeselection unit 130 is formed of a switch. The switch is a slide typeswitch or a button type switch, but it is not limited to types of theswitch.

The charging connector 20 is formed of an attaching-detaching type forsuitably exchanging the portable electronic device or the chargingconnector 20 can include a separated auxiliary connector electricallyconnected thereto.

A front bottom side of the housing is protruded to the front side, so asto form a supporting portion 100, and a speaker 140 is configured insideof the housing. According to an embodiment of the present invention, amicrophone 150 is configured on the top of the housing, but the locationof the microphone 150 is not limited. Further, the microphone cannot beincluded and an externally installed microphone can be used. In casethat the externally installed microphone is used, a microphoneconnecting terminal (not shown) can be configured at a given location ofthe housing. Further, the microphone connecting terminal for connectingan externally installed microphone and a microphone 150 can beconfigured together.

The speaker 140 and the microphone 150 can be electrically connected toan audio signal input/output unit of the portable electronic device.According to an embodiment of the present invention, the batteryremaining display unit 80, the hands-free selection unit 130, thespeaker 140, and the microphone 150 can be selectively configuredtogether or can be partly combined thereof.

Inserting ribs 110 are formed on both lateral sides of the housing forinsertedly fixing the portable electronic device. Therefore, aninserting unit 120 including the supporting portion 100 and theinserting ribs 110 can stably fix the portable electronic device not toeasily be detached.

FIG. 6 is a schematic diagram of a housing of the external battery packaccording to another embodiment of the present invention.

FIG. 6(a) is a schematic front side diagram of the housing of theexternal battery pack. FIG. 6(b) is a schematic lateral side diagram ofthe housing of the external battery pack.

Inserting ribs 110 are formed of both lateral sides of the housing. Aplurality of fixing hooks 225 movable in a perpendicular direction areincluded in inserting ribs 110. According to an embodiment of thepresent invention, it is preferable to include at least two fixing hooks225 in the both lateral sides of the rib 110. Each hook 225 is locatedon the each inserting rib 110. When a portable electronic device isinserted in an inserting portion 120 having the supporting portion 100and inserting ribs 110, the fixing hooks 225 are also inserted inside bypushing of the portable electronic device. Next, dent parts (not shown)formed at lateral sides of the portable electronic device are fixed infixing hooks 225 by pushing back from the housing, thereby stably fixingthe portable electronic device.

As shown in FIG. 6(b), one part of the pen type fixing unit 90 is fixedby a pin 230 and installed to pull toward the housing, thereby stablyfixing at clothing or a belt.

FIG. 7 is a schematic diagram of a housing of the external battery packaccording to another embodiment of the present invention.

FIG. 7(a) is a schematic front side diagram of the housing of theexternal battery pack. FIG. 7(b) is a schematic lateral side diagram ofthe housing of the external battery pack.

As shown in FIG. 7, a detaching protection unit 200 includes a detachingprotection jaw 180 and at least one connection bar 190 connected to thedetaching protection jaw 180. At least one groove 210 corresponding tothe at least one connection bas 190 is formed in the top area of thehousing and the connection bar 190 can be vertically movable in thegroove 210. One side of a spring 220 is fixed inside of the groove 210,and the other side of the spring 220 is fixed to the connection bar 190.

A user pulls the detaching protection unit 200 upwardly and inserts andfixes a portable electronic device in the inserting area 120. Next, whenthe detaching protection unit 200 is released, the top part of theportable electronic device is pulled downwardly, thereby fixing the toppart of the portable electronic device. Therefore, the portableelectronic device can be protected to be detached upwardly from thehousing.

In the drawing, even though the detaching protection unit 200 describesto include two connecting bars 190, it is not limited to include oneconnecting bar 190 installed at substantially the center of thedetaching protection jaw 180 or a plurality of connecting bar 190.Further, according to an embodiment of the present invention, the spring220 can be replaced another elastic material for connecting thedetaching protection unit 200 and the housing.

INDUSTRIAL APPLICABILITY

The advantages of the external battery pack according to an embodimentof the present invention, which were described above, will now besummarized.

First, as the external battery pack includes an output circuit unit,which outputs a constant voltage and a constant current, the externalbattery pack can supply driving power source with a portable electronicdevice and can concurrently charge an internal battery in the portableelectronic device.

Second, as the external battery pack includes a battery remainingdisplay circuit unit and a battery remaining display unit, and thebattery remaining display unit 80 displays a battery remaining statusinto various levels according to a battery remaining status, therebyeffectively using the external battery pack according to the batteryremaining status.

Third, as a charging circuit unit and an output circuit unit can beconfigured to make one unit, and the charging circuit unit or the outputcircuit unit can be commonly used, the battery pack can be made of asmaller size or the secondary battery can have larger capacitance.

Fourth, as a pen type fixing unit is used, a portability of the externalbattery pack can be improved.

Fifth, as an external battery pack includes an inserting unit to insertthe portable electronic device, the external battery pack and theportable electronic device can be combined, thereby a portability of theexternal battery pack can be improved.

While the present invention has been particularly shown described withrespect to preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in the form and details may bemade without departing from the spirit and scope of the invention asdefined by the appended claims.

1. An external battery pack comprising: a secondary battery; an internal circuit; a housing having the secondary battery and the internal circuit; and an inserting portion formed in the housing, wherein the inserting portion is capable of inserting and fixing an portable electronic device.
 2. The external battery pack of claim 1, wherein the external battery pack further comprises a pen type fixing unit having a holding part, the pen type fixing unit is formed at a rear side of the housing for being held on clothing or a belt.
 3. The external battery pack of claim 1 or claim 2, wherein the inserting portion comprises a supporting portion on a front bottom side of the housing and an inserting rib on both lateral sides of the housing.
 4. The external battery pack of claim 3, wherein the inserting portion further comprises a fixing hook capable of moving in a vertical direction.
 5. An external battery pack of claim 3, wherein the inserting portion further comprises a detaching protection portion capable of moving up and down, the detaching protection portion is connected to an elastic material installed in the housing.
 6. The external battery pack of claim 2, wherein the internal circuit comprises: a charging connector for receiving power source; a charging circuit unit for charging the secondary battery by converting the received power source into constant voltage; and a power source output connector for outputting the charged voltage in the secondary battery into one of an power source input terminal of the portable electronic device and a charging connection terminal of a battery of the portable electronic device.
 7. The external battery pack of claim 6, wherein the internal circuit further comprises a DC/DC voltage converting circuit for converting an inputted voltage from the secondary battery into a given level of DC voltage.
 8. The external battery pack of claim 7, wherein the internal circuit further comprises an output circuit unit for outputting the inputted power source from the DC/DC voltage converting circuit, the inputted power source maintains constant voltage and constant current.
 9. The external battery pack of claim 2, wherein the internal circuit comprises: a charging connector for receiving power source supply; a DC/DC voltage converting circuit for converting an inputted voltage from the secondary battery into a given level of DC voltage; and a power source output connector for outputting the given level of DC voltage in the DC/DC voltage converting circuit into one of an power source input terminal of the portable electronic device and a charging connection terminal of a battery of the portable electronic device.
 10. The external battery pack of claim 9, wherein the internal circuit further comprises an output circuit unit for outputting the inputted power source maintaining constant voltage and constant current from the DC/DC voltage converting circuit, wherein the output circuit unit is configured between the DC/DC voltage converting circuit unit and the power source output connector.
 11. The external battery pack of claim 6, wherein the internal circuit further comprises a protecting circuit unit for protecting electrical performance of the secondary battery.
 12. The external battery pack of claim 2, wherein the internal circuit comprises: a charging connector for receiving power source supply; a charging circuit unit for charging the secondary battery by converting the received power source into constant voltage; a protecting circuit unit for protecting electrical performance of the secondary battery, the protecting circuit unit being electrically connected between the charging connector and the charging circuit unit; a DC/DC voltage converting circuit for converting an inputted voltage from the protecting circuit unit into a given level of DC voltage; an output circuit unit for outputting the inputted power source maintaining constant voltage and constant current from the DC/DC voltage converting circuit. a power source output connector for outputting the given level of DC voltage in the DC/DC voltage converting circuit into a charging connecting terminal of a battery of the portable electronic device; a battery remaining display circuit unit for detecting a battery charge remaining status of the secondary battery; a battery remaining display unit for displaying a battery charge remaining status according to a signal inputted from the battery remaining display circuit unit.
 13. The external battery pack of claim 12, wherein the charging circuit unit and the outputting circuit unit are combined to be a charging/outputting circuit unit and the internal circuit further comprises a circuit converting connector for converting a circuit wire connection according to electrical connections between the charging circuit unit and the internal circuit, and between the outputting circuit unit and the internal circuit.
 14. The external battery pack of claim 2, wherein the inserting portion comprises a supporting portion on a front bottom side of the housing and an inserting rib on both lateral sides of the housing.
 15. The external battery pack of claim 14, wherein the inserting portion further comprises a fixing hook capable of moving in a vertical direction.
 16. An external battery pack of claim 14, wherein the inserting portion further comprises a detaching protection portion capable of moving up and down, the detaching protection portion is connected to an elastic material installed in the housing.
 17. The external battery pack of claim 7, wherein the internal circuit further comprises a protecting circuit unit for protecting electrical performance of the secondary battery.
 18. The external battery pack of claim 8, wherein the internal circuit further comprises a protecting circuit unit for protecting electrical performance of the secondary battery.
 19. The external battery pack of claim 9, wherein the internal circuit further comprises a protecting circuit unit for protecting electrical performance of the secondary battery.
 20. The external battery pack of claim 10, wherein the internal circuit further comprises a protecting circuit unit for protecting electrical performance of the secondary battery. 